Mr Moynihan said in making his decision, he had to balance the obvious public interest "in the due prosecution and conviction of offenders with the views of the victims or their families".

He also considered the "significant period of time" since the offences were alleged to have been committed, as well as the two-and-a-half years that Patel had spent in custody.

Mr Moynihan also factored in the "substantial cost of very complex litigation".

"The fact that in the re-trials the defence has presented credible evidence from medical experts and the Crown has not been able to satisfy the requirement of proving the alleged negligence to the criminal standard," he said.

He said Patel was also charged with eight counts of fraud.

The DPP said it was in the public interest to proceed with four of those charges.

"On the evidence, adequately reflect the criminality involved in the allegation that Jayant Patel dishonestly obtained registration and employment as a doctor in Queensland," he said.

"Those matters are still before the courts and I do not intend to make any further comment."